The present invention relates to chair structures, for example to a chair offering a sitting comfort that is suitable for operations in an office or the like.
Conventionally, there exist chairs of the type which is capable of rearwardly inclining a whole backrest portion as chairs for use in offices or the like. Usually, the backrest portion of such a chair is inclined rearwardly by releasing a lever provided under the seat, pressing the backrest portion rearwardly and returning the lever to its original position at a desired angle of inclination to make the backrest portion stationary.
Since such a chair is configured to allow its whole backrest portion to incline rearwardly, the chair involves a problem that the shoulders of a person sitting on the chair come to abut a frame portion of the chair and hence are restrained from moving when the sitting person wants to be refreshed by stretching his or her back or when the need arises to bend the upper part of his or her body rearward as in the case where the sitting person is going to pick up baggage placed behind by turning the shoulders with the chair kept in an upright state.
Accordingly, it is an object of the present invention to provide a chair which allows a person sitting thereon to freely move the upper part of his or her body, thereby resolving the foregoing problem.
To resolve the foregoing problem, the present invention provides a chair capable of switching between a state that allows a whole backrest portion thereof to incline rearwardly and a state that allows an upper part of the backrest portion to incline rearwardly relative to a lower part of the backrest portion.
With such a construction, a person sitting on the chair can selected a desired one of the state allowing the sitting person to stretch his or her whole body for relaxing and the state allowing the sitting person to free a part of his or her body adjacent the shoulders by inclining the upper part of the backrest portion rearwardly relative to the lower part thereof. Adoptable methods of rearwardly inclining the upper part of the backrest portion include: a method such as to incline the upper part of the backrest portion rearwardly with the lower part of the backrest portion kept in an upright position; a method such as to incline the whole backrest portion rearwardly and then incline only the upper part of the backrest portion further rearwardly; and like methods.
In the case of the arrangement that allows the whole backrest portion to incline rearwardly, if a seat portion is also allowed to incline rearwardly at the same time, the chair allows a person to sit thereon more deeply when the whole backrest portion is inclined, thereby offering a better sitting comfort.
Among such inventions, the invention that allows the upper part of the backrest portion to incline rearwardly with the lower part of the backrest portion fixed in an upright position, allows the sitting person to largely bend the backbone rearwardly, thereby making the sitting person more refreshed.
In the arrangement that allows the upper part of the backrest portion to incline rearwardly, if a part of the backrest portion above the waist of the sitting person is allowed to incline rearwardly, the chair allows the sitting person to bend his or her whole backbone as well as the neck portion rearwardly.
Further, such a construction is possible that the chair comprises a link member rotatably mounted on a support base, a backrest frame rotatably connected to the link member, and a pin removably inserted though holes that are defined in the link member and the backrest frame, respectively, wherein the link member and the backrest frame become rotatable as an integral part when the pin is inserted through the two holes, while when the pin is pulled out of one of the two holes, the backrest frame becomes independently rotatable.
With such a construction, it is possible to allow the link member and the backrest frame to incline rearwardly as an integral part by inserting the pin through the holes thereof or to allow the upper part of the backrest frame to relatively incline rearwardly independently of the link member by pulling the pin out of one hole. The chair of this construction allows a person sitting thereon to stretch his or her whole body to relax the whole body as well as to bend the backbone reversely thereby making the sitting person refreshed. Adoptable methods of inclining the upper part of the backrest portion include: a method such as to incline the upper part of the backrest portion rearwardly with the lower part of the backrest portion kept in an upright position; and a method such as to incline the whole backrest portion rearwardly and then incline only the upper part of the backrest portion further rearwardly.